1. Field of the Invention
The present invention relates to an endoscope, having an outer tube that is joined to an optical head that carries an eyepiece cup or an adapter device for a camera system or an integrated miniature camera, also having an inner tube, arranged in the outer tube and extending into the optical head and supported there, that carries optical components, the outer tube and inner tube being rigidly and sealingly joined to one another at the distal end of the endoscope.
2. Related Prior Art
Endoscopes of this kind are commonly known, and are marketed in this configuration, for example, by the Applicant.
Optical components, for example rod lenses, are arranged in the inner tube; further components extend into the optical head. It is possible to observe through the optical system from the proximal end of the eyepiece cup, which has a window. In other embodiments, instead of the eyepiece cup an adapter device for a camera is provided, or a miniature camera is directly integrated. These three embodiments represent an observation element of the optical head. The outer tube, which surrounds the inner tube, delimits an annular space around the outer side of the inner tube that serves to guide light guides, for example glass fibers, to the distal end of the endoscope in order to illuminate the point being observed. The glass fibers are usually conveyed into this annular space via a radially protruding fitting on the optical head. At the distal end, the outer tube and inner tube are immovably joined to one another via a sealed join, so that no liquids or gases can penetrate into the interior of the endoscope from that end.
After operations have been performed the endoscopes must be sterilized, for which purpose they are heated in autoclaves to temperatures in the range from 130 to 140xc2x0 C.
Now that minimally invasive procedures have become routine and, for example in hospitals, numerous endoscopically observed operations are performed every day, the endoscopes are in frequent use and are consequently subjected to severe mechanical stresses, especially during autoclaving. In order for endoscopes to be available again as quickly as possible after operations, so-called xe2x80x9cflash autoclavesxe2x80x9d have been developed, in which all of the endoscopes are heated to 143xc2x0 C. and then quenched with cold water. These extreme temperature changes must be handled from a mechanical standpoint so that thermal expansion does not cause any damage to the optical system, for example causing it to leak and allowing moisture to penetrate into the optical system. An expansion compensation capability must therefore be created for such temperature shocks. This compensation capability is substantially a longitudinal expansion compensation capability for the elongated endoscopes.
In one known solution, the proximal end of the outer tube is mounted in axially movable fashion in the optical head, and a corresponding O-ring provides sealing closure. This creates a longitudinal expansion compensation capability in response to the aforementioned temperature shocks.
A disadvantage of this design is that because of the movable mounting arrangement, the mechanical stability of the join between outer tube and optical head cannot be guaranteed for the long term. A torque acts on the joining point when an endoscope is set down, since the optical head usually has a greater diameter than the outer tube and transitions via a step into the slender endoscope shaft. If this join between the outer tube and optical head loosens, not only is mechanical stability impaired, but there is also the possibility that moisture may penetrate into the interior of the optical head and damage the optical system.
In a further known design as disclosed by the company styled Richard Wolf GmbH, Germany, the proximal end of the inner tube is supported sealingly via an O-ring, but in axially movable fashion, on the inner side of the optical head. If this sealing point becomes leaky as a result of numerous longitudinal expansions during autoclaving cycles, there exists the risk that moisture may penetrate directly into the inner tube and thus into the optics.
It is therefore the object of the present invention to provide an endoscope remaining mechanically stable over a long term, in particular even after numerous flash autoclaving cycles, and having longitudinal expansion capability, without the possibility for contaminants to penetrate into the optical components.
According to the present invention, the object is achieved in that outer tube, optical head, and observation element are fitted together to form an immovable first module that is sealed among these parts but not closed off from the outside; and that at its proximal end the inner tube is immovably and sealingly fitted together with a housing that hermetically closes off the optical components, to form a second module.
Because the outer components, namely the outer tube, optical head, and observation elements (eyepiece cup, or adapter, or integrated miniature camera) are fitted together into a fixed module, mechanical effectsxe2x80x94whether due to mechanical impacts when the unit is set down, or handling, or expansion effects in response to thermal shockxe2x80x94cannot result in any relative displacements of the components in this rigid assemblage. The latter possesses long-term dimensional stability, and the individual componentsxe2x80x94outer tube, optical head, and eyepiece cupxe2x80x94remain immovably and nondisplaceably fitted to one another. The fact that fitting is accomplished in such a way that these parts are fitted sealedly together with one another creates a module into which moisture, gases, or other contaminants cannot enter from the outside, with the exception of the two openings on the ends.
Because of the fact that at its proximal end, the inner tube is immovably and sealingly fitted together with a housing that hermetically closes off the optical components, forming a second module, the optical elements are hermetically sealed off from the outside world, so that no contaminants, whether gaseous or liquid, can penetrate into the optical system.
These two modules are rigidly and sealedly joined to one another at the distal end. At the proximal end, the inner tube and the proximal end of the hermetically sealing housing are then supported in the optical head. The longitudinal expansions or shrinkages of the two elongated modules that occur in response to temperature shocks can now take place in undisturbed fashion alongside one another, proceeding from the fixed distal linkage point between these two modules. Unequal longitudinal expansions of the modules can now be permitted by way of relative movements between them. This relative movement on the one hand does not result in any impairment of the mechanical stability of the endoscope, since the latter is substantially secured by the external enveloping assemblage of the first module made up of the outer tube, optical head, and eyepiece cup. This relative movement also cannot result in leaks in the optical system, since the inner second module is hermetically sealed within itself. In the optical head, sealing measures are taken in a manner known per se, for example by way of O-rings, between the outer side of the inner second module and the inner side of the outer first module, so that water or steam cannot penetrate during autoclaving. If this should nevertheless happen, it is not detrimental to mechanical stability nor does it have any negative influence on the optical system, since the latter is, as such, hermetically sealed.
In an embodiment of the invention, the proximal end region of the second module is supported in floating fashion in the optical head.
The advantage of this feature is that this floating mounting system, which is nevertheless sealed in terms of the penetration of autoclaving steam or liquid, allows jam-free longitudinal expansion in response to temperature shocks and also makes it possible for radially acting mechanical shocks or impacts, when an endoscope is set down or inadvertently dropped, to be absorbed or distributed in such a way that no damage occurs to the optical system. The optical system contains numerous lenses, for example relatively long rod lenses made of glass materials, that could possibly break in the event of intense mechanical shocks. The floating mounting system allows such shocks to be absorbed more gently or in more damped fashion, thereby considerably extending the life span of the lens system.
In a further embodiment of the invention, the proximal end region of the second module is supported in stationary fashion on the optical head and is equipped with expansion features.
In contrast to the embodiment described previously, in which the inner second module can displace in the proximal direction, this capability does not exist here because of the stop, and the longitudinal compensation capability is provided by way of the expansion features. In this case the proximal end of the inner module can be permanently held at a very specific point; this end is usually closed off with a glass window or lenses in order to ensure visibility through the inner tube. Readjustments of the optics due to relative motion are no longer necessary. The necessary longitudinal expansion is brought about via the expansion features.
In a particularly preferred embodiment of this design, the expansion feature consists in a bellows-like configuration of the wall of the housing.
The bellows absorbs the requisite changes in shape when expansion or shrinkage events occur, so that the other components, especially the lenses, remain in an unchangeable position relative to one another.
In a further embodiment of the invention, both the immovable sealed join among the individual components of the two modules and the join between the modules at the distal end are accomplished by soldering, welding, or adhesive bonding.
The advantage of this feature is that with the use of common working methods it is possible to create not only the corresponding mechanical bond between the parts that are to be joined, but also the correspondingly sealed join that withstands, over the long term, both mechanical shocks and temperature shocks.
It is understood that the features mentioned above and those yet to be explained below can be used not only in the respective combinations indicated, but also in other combinations or in isolation, without leaving the context of the present invention.